In high energy efficient water heaters and furnaces, waste gases of combustion are passed in heat transfer relation with water or air to extract heat from the combustion gases. Cooling of the combustion gases through heat transfer results in the production of substantial quantities of condensate and it is necessary to discharge the condensate without allowing escape of the combustion gases into the surrounding building.
In the past, various types of condensate discharge devices have been employed in steam or compressed air systems to permit the discharge of condensate while preventing escape of the gas. One form of condensate discharge device, as used in the past has been a P-trap. While devices of this type are effective to discharge condensate without permitting the gas to enter the environment, foreign materials or contaminants tend to collect in the trap and eventually clog the line and prevent operation.
Other types of condensate discharge devices are complicated structures requiring numerous moving parts which can be subject to corrosion by contaminates in the waste gas.